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Thermal infrared remote sensing and Kirchhoff's law: 1. Laboratory measurementsKirchoff's Law, as originally conceived, applies only to samples in thermal equilibrium with their surroundings. Most laboratory measurements of emissivity only approach this condition and it never applies in remote sensing applications. In particular, the background is often much cooler than the radiating sample, and this has led to a long controversy about the applicability of Kirchhoff's Law under such conditions. It has also led to field and laboratory measurement techniques that use some form of the 'emissivity box' approach, which surrounds the sample with a background as close as possible to the sample temperature. In our experiments, we have heated soil samples in air on a hot plate in the laboratory to a much higher temperature than the room temperature background. Spectral emissivity was measured, except the known emissivities of both the primary and secondary Christiansen features were used, instead of assuming an emissivity of unity at these wavelengths. The results from this investigation are discussed in brief.
Document ID
Document Type
Conference Paper
Salisbury, J. W.
(Johns Hopkins Univ. Baltimore, MD, United States)
Wald, A.
(Johns Hopkins Univ. Baltimore, MD, United States)
Daria, D. M.
(Johns Hopkins Univ. Baltimore, MD, United States)
Date Acquired
September 6, 2013
Publication Date
January 1, 1993
Publication Information
Publication: Lunar and Planetary Inst., Twenty-Fourth Lunar and Planetary Science Conference. Part 3: N-Z
Subject Category
Inorganic And Physical Chemistry
Accession Number
Distribution Limits
Work of the US Gov. Public Use Permitted.

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